This invention relates generally to the art of coaxial connectors, and more specifically to an improvement in the structure of an inner conductor terminal of a female coaxial transmission line connector.
One commonly used type of coaxial connector utilizes for the inner conductor a pin as part of the male connector portion and a hollow tube as part of the female connector portion. The pin is removably placed in the tube when the connector portions are fastened together. The tube is slotted along its length beginning at its end and the resulting fingers are resiliently loaded to tightly grip the pin when inserted into the tube. A disadvantage of this type of connector is that the actual diameter of the inner conductor changes abruptly and the slots in the tube present a further effective change in diameter, all of which causes a impedance change in the cable and presents a missmatch to radio frequencies. The slots are kept as short as possible and typically are two to four in number in order to reduce the undesirable impedance missmatch but this results in contact being made with the pin at very small surface areas with a large pressure resulting between the inside of the tube and the outside of the pin. This causes excessive wear and, eventually, poor electrical contact. Furthermore, any misalignment of the mating pin and tube will cause one of the tube fingers to distort or break if the misalignment is sufficient.
The above type of connector pair is termed "sexed" and represents the overwhelming majority of connectors presently used for coaxial transmission line applications. Two other of connector arrangements are available without sexed interfacing parts.
One "sexless" interface is commonly used for high power interconnects. The inner conductors are hollow at the joint and a compressive conductive bullet is inserted into both hollow ends. Thus, the joining center conductors are smooth cylindrical surfaces without the axial slots found on the female "sexed" connector.
Another "sexless" connector pair is the General Precision Connector (GPC). In this connector arrangement, the outer conductors meet in a butt joint that is aligned and compressively held with carefully controlled tolerances by an outer coupling mechanism. The center conductors are aligned and held in the air dielectric interface by preceeding solid dielectric beads. The conductive center conductor interface is made by spring loaded extending collets located within each end section. This General Precision Connector provides repeatable connections with low interface reflection and loss that are essential high accuracy standards of measurement.
Associated with the above is the Laboratory Precision Connector (LPC) which does not include a dielectric support for the inner conductor. Two LPC's do not mate, only the LPC to a GPC joint is possible. The LPC center conductor is held and aligned by the center conductor of the GPC connector. The LPC interface does not have the supporting bead that causes reflection and, often, an upper frequency limit due to a higher order mode cavity resonance. The LPC is generally utilized in precision measurement laboratory configurations.
Since 1960 there has been a rapidly expanding use of a small and simplified connector for the increasing complex microwave system utilized in space and missile programs. The availability of miniature connectors which are mechanically rugged and low reflection has exerted a major influence on microwave circuit design in these years. Systems and components can be miniaturized with generally improved electrical performance. Miniature connectors allow packaging flexibility in both coaxial and stripline designs. The smaller size and improved performance have also opened up the frequency range of 12 to 40 GHz for coaxial circuitry.
The miniature connectors for use in the 12 to 40 GHz range, notably the SMA type, have a poor record of performance and repeatability with multiple interconnections. Measurement performance has been severely limited by the short lifetime of the miniature connector on the measurement instrument port. Often the measurement is made through an adapter between a larger, more reliable connector to the miniature connectors. Then, the adapters are frequently replaced.
Therefore, it is a principal object of this invention to provide a connector interface to the standard miniature connectors that provides low reflection, longer life and parts that subject to wear and damage are replaceable.